JP2003085835A - Method of manufacturing draw type optical disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a DRAW type optical disk substrate which is formed by using a transesterification process polycarbonate, is little in the warpage of the substrate, small in the birefringence of the substrate, free of bright defects and free of defects in dye coating application, and method of manufacturing the DRAW type optical disk substrate. SOLUTION: This method of manufacturing the DRAW type optical disk substrate is constituted by forming a dye recording layer by application of dye onto the molded substrate obtained by injection molding the polycarbonate resin of 10,000 to 23,000 in viscosity average molecular weight manufactured by the transesterification process from an aromatic hydroxyl compound and diester carbonate and forming grooves on its signal surface, is characterized in that the contact angle of water drops measured by the signal surface before the formation of the dyestuff recording layer is 77 to 85 deg. and ionizing air of a positive polarity is blown in the direction parallel to the substrate surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a write-once type optical disc substrate which is a high density storage medium. In particular, the present invention relates to a method for manufacturing a write-once optical disc substrate using an organic dye in the optical recording layer and a method for manufacturing a write-once optical disc using an organic dye in the optical recording layer.

[0002]

2. Description of the Related Art An optical disk has been rapidly increasing in production in recent years as an information recording medium of low cost and high density recording capacity. Especially CD-R (write-once compact disc) and D
A write-once optical disc called a VD-R (write-once digital versatile disc) has a high capacity and is being reduced in price with rapid spread. Therefore, the improvement of the signal characteristics and the productivity of the substrate are becoming more important. Further, further densification is expected in the future.

CD which adopts an optical recording method using a laser
In -R and DVD-R, data can usually be recorded only once, and digital information is stored in the form of marks or pits of high optical density against a reflective background and read by convergent laser light.

Thermoplastic amorphous resins generally used for optical disk transparent substrates are polycarbonate, polymethylmethacrylate, amorphous polyolefin, etc., but in view of strength, heat resistance, dimensional stability, low cost, etc. Polycarbonate is commonly used. In particular, polycarbonate produced by an ester exchange method from an aromatic dihydroxy compound and a carbonic acid diester is environmentally friendly because it does not use phosgene gas or an organic solvent, as compared with polycarbonate produced by an interfacial method which has been widely used in the past. Is less loaded. Further, since the manufacturing process is simplified as compared with the interface method, there is a great merit that a product of stable quality can be obtained. Furthermore, it has the advantage of being able to convert the raw material monomer from the by-product generated by the transesterification reaction, and is suitable for resin for optical disk substrates because it has the advantages of environmental friendliness, stable quality, and low cost.

A disadvantage of the aromatic polycarbonate is that it has a poor meltability during injection molding due to its high melt viscosity. Therefore, the transferability of the signal is poor, and the birefringence due to the strain inside the substrate becomes large, which causes an error in the signal reproduction. By transferring a high-density signal to the substrate, or reducing the viscosity average molecular weight of the polycarbonate in order to reduce birefringence caused by strain inside the substrate,
This is possible because the melt viscosity at the time of molding is lowered and the fluidity is improved. However, if the molecular weight of the polycarbonate is lowered too much, another problem that the strength of the substrate is lowered occurs. On the other hand, if the molecular weight is too high, the strength and heat resistance are improved, but the melt viscosity at the time of molding becomes high, which causes a decrease in transferability and an increase in birefringence. Therefore, an aromatic polycarbonate having an appropriate molecular weight is required.

It is known that the injection-molded optical disk substrate manufactured by the transesterification method has a property of being easily charged to a negative polarity as compared with the polycarbonate manufactured by the interfacial method (Japanese Patent Laid-Open No. 11- 27939
6). It is stated in the patent that when the surface of the optical disk substrate is negatively charged, dust in the air is likely to adhere, and the wettability of the dye of the write-once type optical disk is deteriorated.
Some ideas have been proposed for adding some types of antistatic agents. However, the addition of an antistatic agent to polycarbonate is not desirable because it causes a drawback that transparency is deteriorated and that it is easily decomposed when exposed to high temperature and high humidity for a long time. Also, US Pat.
22, 943 and U.S. Pat. No. 6,140,457 propose a method of reducing the charge by modifying the molecular ends of a polycarbonate resin. However, only by modifying the terminal structure of the resin, the peeling charge at the time of releasing from the stamper can be reduced, but it is not sufficient to completely remove the transfer charge generated during the substrate manufacturing process. Heretofore, there have been proposed some methods for removing electric charges during the manufacturing process of an optical disk. Japanese Unexamined Patent Publication No. 6-203414 proposes to ionize the air used for releasing the substrate from the stamper, but the transfer charge generated after being taken out from the mold cannot be removed. Further, Japanese Patent Laid-Open No. 6-60630 proposes to blow out ionized air in order to remove the charge on the substrate inside the drive which is the reproducing / recording device, but it is not effective for the charge before applying the dye. There is no. JP-A-7-57307
Proposes to remove the charge on the substrate surface with a charge-removing bar or an ionizer after it is taken out from the mold. Not mentioned. Further, in Japanese Unexamined Patent Publication No. 10-177744, there is proposed a method of discharging electricity by spraying air containing ions having a polarity opposite to the polarity of the charge on the substrate surface. No improvement in coatability of dyes or dyes is mentioned, or in Japanese Patent Laid-Open No. 5-298746, a method is proposed in which an antistatic film is applied to the inner hole of the disc to leak static electricity to the spindle of the stock portion of the disc. However,
Since it is necessary to apply an antistatic film on the surface of the substrate, the cost increases and the process becomes complicated. Therefore, no method has been found for completely removing the electrostatic charge on the substrate using the transesterification polycarbonate before the dye coating.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is a substrate made of a polycarbonate produced by a transesterification method, the substrate having a small warp, a small birefringence, no bright defects, and no defective dye coating. Another object is to provide a method for manufacturing a write-once optical disc substrate and a method for manufacturing a write-once optical disc.

[0008]

As a result of intensive studies by the present inventors, the charging phenomenon on an optical disk molding substrate depends on the water droplet contact angle on the substrate surface, and if the water droplet contact angle is less than a certain value, charging is likely to occur. It was found that the electrification causes deformation of the write-once optical disc when the dye solution is dropped. That is, it has been found that the charge is reduced by adjusting the contact angle of water droplets on the surface of the substrate to a certain value or more, and the deformation at the time of dropping the dye solution is eliminated. At the same time, it was found that by spraying ionized air of positive polarity in the direction parallel to the substrate surface immediately before applying the dye of the write-once optical disc, it is possible to completely remove the charge generated during the transfer. The present inventors have invented a write-once optical disc substrate having good signal characteristics and productivity based on the above findings.

That is, according to the present invention, the viscosity average molecular weight produced from an aromatic dihydroxy compound and a carbonic acid diester by a transesterification method is 10,000 to 23,000.
A method of manufacturing a write-once type optical disc substrate, comprising: forming a dye recording layer by applying a dye to a molded substrate having a groove formed on a signal surface by injection-molding a polycarbonate resin of 0. A write-once optical disc substrate having a contact angle of water droplets measured on the previous signal surface of 77 ° or more and 85 ° or less, and blowing ionized air of positive polarity in a direction parallel to the substrate surface before dye coating. Exists in the manufacturing method of.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Aromatic Polycarbonate In the present invention, the viscosity average molecular weight of the aromatic polycarbonate must be in the range of 10,000 to 23,000. When the viscosity average molecular weight is less than 10,000, the strength of the substrate is significantly lowered, and when it exceeds 23,000, birefringence during injection molding is significantly increased, which is not desirable. The viscosity average molecular weight is preferably 1400.
It should be chosen between 0 and 18,000. The viscosity average molecular weight (M) here is calculated from the Schnell's viscosity formula shown below by measuring the intrinsic viscosity (η) at 20 ° C. of a solution using methylene chloride as a solvent using an Ostwald viscometer. [Η] = 1.23 × 10 ⁻⁴ M ^0.83 Therefore, when the polycarbonate is a polymer mixture, the viscosity average molecular weight of the polymer mixture is determined.

The aromatic polycarbonate used in the present invention can be obtained by transesterification using an aromatic dihydroxy compound and a carbonic acid diester as raw materials in the presence of a transesterification catalyst. The aromatic dihydroxy compound is usually represented by the following formula (1).

[0012]

[Chemical 1]

(In the formula, A is a single bond, an alkylene group having 1 to 8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, and 5 carbon atoms.
To C15 cycloalkylene group, C5 to C15 cycloalkylidene group and -O-, -S-, -CO-, -S
O- and -SO ₂ - are those selected from the group consisting of divalent groups represented by, X and Y is halogen or a hydrocarbon group having 1 to 6 carbon atoms, p and q are 0 It is an integer of 2, and X and Y, and p and q may be the same or different. ) Examples of the aromatic dihydroxy compound represented by the above formula (1) include bis (4-hydroxydiphenyl) methane, 2,2-bis (4-hydroxyphenyl) propane, and 2,2-bis (4-hydroxy). -3-Methylphenyl) propane, 2,2-bis (4-hydroxy-3-t)
-Butylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2
-Bis (4-hydroxy-3,5-dibromophenyl)
Propane, 4,4-bis (4-hydroxyphenyl) heptane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4′-dihydroxybiphenyl, 3,
3 ', 5,5'-tetramethyl-4,4'-dihydroxybiphenyl, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ether, bis (4- Examples thereof include hydroxyphenyl) ketone, and particularly preferably 2,2-bis (4-hydroxyphenyl) propane (hereinafter abbreviated as “bisphenol A”). These aromatic dihydroxy compounds are used alone or even 2
It may be a mixture of two or more species.

The carbonic acid diester is represented by the following formula (2).

[Chemical 2]

(In the formula, A'is an aliphatic group having 1 to 18 carbon atoms, a substituted aliphatic group or an aromatic group, and two A'may be the same or different.) Examples of the carbonic acid diester represented by the above formula (2) include aliphatic carbonates such as dimethyl carbonate, diethyl carbonate and di-t-butyl carbonate, and aromatic carbonates such as diphenyl carbonate and biphenylphenyl carbonate. However, diphenyl carbonate is particularly preferable, and these carbonic acid diesters may be used alone or in combination of two or more kinds.

The aromatic polycarbonate used in the present invention is produced by a transesterification method, particularly bisphenol A is used as the aromatic dihydroxy compound, diphenyl carbonate is used as the carbonic acid diester, and a molar ratio of diphenyl carbonate / bisphenol A1 is used. 1.
It is preferred to use the transesterification method with an amount of 001 to 1.3, preferably 1.02 to 1.2. If the molar ratio is less than 1.001, the content of terminal hydroxyl groups in the produced aromatic polycarbonate tends to increase, and the thermal stability of the polymer tends to deteriorate.
If it becomes larger, the rate of the transesterification reaction will decrease under the same conditions, and it tends to be difficult to produce an aromatic polycarbonate having a desired molecular weight.

A transesterification catalyst is used in the production of the above aromatic polycarbonate. An alkali metal compound and / or an alkaline earth metal compound is used as the catalyst, and a basic compound such as a basic boron compound, a basic phosphorus compound, a basic ammonium compound, or an amine compound can also be supplementarily used. However, in terms of physical properties and handling, it is particularly preferable to use the alkali metal compound and / or the alkaline earth metal compound alone.

The amount of the catalyst is the aromatic dihydroxy compound
1 x 10 for 1 mol of product^-7~ 9 × 10^-7Molar range
It is preferably used in, more preferably 1.5 ×
10 ^-7~ 8 × 10^-7In the molar range, particularly preferably 2 ×
10^-7~ 7 × 10^-7Used in the molar range. This amount
If the amount is less than the specified value, it will be
The polymerization activity required to produce carbonate is not obtained.
Above this amount, the polymer hue
Deteriorates, the number of branches increases, and the moldability of the polymer is impaired.
Tend.

Examples of the alkali metal compound include sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, cesium hydrogen carbonate, sodium carbonate, potassium carbonate and carbonic acid. Lithium, cesium carbonate, sodium acetate, potassium acetate, lithium acetate, cesium acetate, sodium stearate, potassium stearate, lithium stearate, cesium stearate, sodium borohydride, potassium borohydride, lithium borohydride, hydride Cesium boron, sodium phenyl boride, potassium phenyl boride, lithium phenyl boride, cesium phenyl boride, sodium benzoate, potassium benzoate, lithium benzoate,
Cesium benzoate, disodium hydrogen phosphate, 2 potassium hydrogen phosphate, 2 lithium hydrogen phosphate, 2 cesium hydrogen phosphate, 2 sodium phenyl phosphate, 2 potassium phenyl phosphate, 2 lithium phenyl phosphate, 2 phenyl phosphate Cesium, sodium, potassium, lithium, cesium alcoholate, phenolate, bisphenol A
2 sodium salt, 2 potassium salt, 2 lithium salt, 2 cesium salt and the like.

As the alkaline earth metal compound,
For example, calcium hydroxide, barium hydroxide, magnesium hydroxide, strontium hydroxide, calcium hydrogen carbonate, barium hydrogen carbonate, magnesium hydrogen carbonate, strontium hydrogen carbonate, calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, calcium acetate, acetic acid. Examples thereof include barium, magnesium acetate, strontium acetate, calcium stearate, barium stearate, magnesium stearate, and strontium stearate.

Examples of the basic boron compound include tetramethylboron, tetraethylboron, tetrapropylboron, tetrabutylboron, trimethylethylboron, trimethylbenzylboron, trimethylphenylboron, triethylmethylboron, triethylbenzylboron and triethylphenylboron. , Sodium salt, potassium salt, lithium salt, calcium salt, barium salt, magnesium salt, strontium salt of tributylbenzylboron, tributylphenylboron, tetraphenylboron, benzyltriphenylboron, methyltriphenylboron, butyltriphenylboron, etc. Is mentioned.

Examples of the basic phosphorus compound include triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine, tributylphosphine,
Examples thereof include quaternary phosphonium salts. As the basic ammonium compound, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylbenzylammonium hydroxide, trimethylphenylammonium hydroxide, Triethylmethylammonium hydroxide, triethylbenzylammonium hydroxide, triethylphenylammonium hydroxide, tributylbenzylammonium hydroxide, tributylphenylammonium hydroxide, tetraphenylammonium hydroxide, benzyltriphenylammonium hydroxide, methyltriphenylammonium hydroxide Sid, butyl triphenyl ammonium hydroxide, and the like.

Examples of amine compounds include 4-aminopyridine, 2-aminopyridine, N, N-dimethyl-4-aminopyridine, 4-diethylaminopyridine,
2-hydroxypyridine, 2-methoxypyridine, 4-
Methoxypyridine, 2-dimethylaminoimidazole,
2-methoxyimidazole, imidazole, 2-mercaptoimidazole, 2-methylimidazole, aminoquinoline and the like can be mentioned.

The transesterification reaction is generally carried out in a multi-step process of two or more steps. Specifically, the reaction in the first step is carried out under reduced pressure of 93 to 1.33 kPa at 120 to 260.
0.1 to 5 at a temperature of 180 ° C., preferably 180 to 240 ° C.
The reaction is carried out for a time, preferably 0.1 to 3 hours. Then,
The polycondensation reaction is finally carried out at a temperature of 240 to 320 ° C. under a reduced pressure of 133 Pa or less while increasing the degree of reduced pressure of the reaction system.

The reaction can be carried out in a batch system, a continuous system, or
Either a batch type or a continuous type may be used, and the apparatus used may be a reactor of any of a tank type, a tube type or a column type.

In the production of the above aromatic polycarbonate, it is preferable to add an acidic compound or a precursor thereof, for example, a sulfonic acid compound or a precursor thereof, as a deactivator in order to deactivate the transesterification catalyst. More specifically, p-toluenesulfonic acid, methyl p-toluenesulfonate, butyl p-toluenesulfonate and the like are particularly preferable. These may be used alone or in combination of two or more.

The amount of these acidic compounds or their precursors is 0.1 to 50 times mol, preferably 0.5 to 30 times mol, relative to the neutralization amount of the basic transesterification catalyst used in the polycondensation reaction. Added. The timing of adding the acidic compound or its precursor may be any time after the polycondensation reaction, and there is no particular limitation on the addition method, and depending on the properties of the acidic compound or its precursor or desired conditions, Any method such as a method of adding, a method of dissolving in a suitable solvent and a method of using a master batch in the form of pellets or flakes may be used.

The aromatic polycarbonate used in the present invention may be added with additives such as a stabilizer, an ultraviolet absorber, a release agent and a coloring agent, as long as the effects of the present invention are not impaired.

Molded substrate A write-once type optical disk such as a CD-R or a DVD-R is a molded substrate formed by injection molding of the above aromatic polycarbonate and having a plurality of concentric guide grooves called grooves. As the material. At the time of this injection molding, the shape of the submicron-sized pits and grooves pre-engraved on a predetermined stamper is the surface of a disk-shaped transparent molded substrate (referred to as "signal surface" in this specification).
It is obtained by faithfully transferring to.

In the present invention, on the molded substrate, the water droplet contact angle measured on the signal surface before the dye recording is formed, preferably,
It is necessary that the water droplet contact angle measured at the flat portion extending inside the groove on the signal surface (referred to as “inner peripheral portion” in the present specification) is 77 ° or more and 85 ° or less. If the contact angle of water droplets on this molded substrate is less than 77 °, it is highly negatively charged and unevenness occurs during dye application. Also, 85
If the temperature exceeds 50 ° C., the wettability of the dye solution and the substrate becomes poor, and bright defects occur due to partial repelling of the coating film. The water drop contact angle is preferably 78 to 79 °.

The details of the method for measuring the water droplet contact angle of the molded substrate are as follows. First, using a microsyringe, one drop of pure water 20 μL, under the environment of 23 ° C. and 50% RH, is formed on the surface of the inner peripheral portion of the molded substrate, preferably within 2 to 3 mm from the innermost peripheral edge of the groove. Drop at a position and measure the contact angle θ at 5 points 30 seconds after dropping with a goniometer, and calculate the average value.

The following methods can be mentioned for increasing the contact angle of water droplets. 1. A hydrophobic group is introduced at the end of the molecular chain. 2. Add an additive that easily exists on the substrate surface and is highly hydrophobic. Method 1 utilizes the fact that molecular chain ends with low free energy tend to condense on the surface. Particularly, when the concentration of the terminal alkyl group component is high, the hydrophobizing effect is high. The method 2 is specifically selected from additives having poor compatibility with aromatic polycarbonate and high hydrophobicity. For example, pentaerythritol tetrastearate, polyolefin, polycaprolactone and the like are desirable.

In order to reduce the water drop contact angle, the above method may be reversed. That is, 3. A hydrophilic group is introduced at the end of the molecular chain. 4. Add an additive that easily exists on the substrate surface and is highly hydrophilic. The method of 3 is preferably a method of hydrophilizing with a terminal hydroxyl group having high free energy. Method 4 is specifically selected from additives having high hydrophilicity. For example, glycerin or the like is desirable.

[0034] as the write-once optical disc write once optical disk representative of, for example, in the molding substrate, a dye recording layer, reflective layer, and protective layer, of the CD-R type is laminated in this order optical disk In addition, a laminate comprising a dye recording layer, a reflective layer, and optionally a protective layer, and a disk-shaped substrate (dummy plate) are attached to the above-mentioned molded substrate with an adhesive so that the recording layer is on the inside. There are a DVD-R type optical disc having a combined structure, and a DVD-R type optical disc having a structure in which the above-mentioned two laminated bodies are bonded together with an adhesive so that their recording layers are inside. In the method of the present invention, the dye recording layer for recording and reading signals in the write-once optical disc is formed by directly applying the dye to the signal surface on the substrate. Further, before the dye is applied, generally, while cooling the injection-molded substrate, ionized air having a positive polarity is blown in a direction parallel to the substrate surface. In the method of the present invention, in particular, while the molded substrate before forming the dye recording layer passes through a plurality of cooling stages while holding the substrate surface substantially horizontally, down-blowing cooling air is directed in a direction perpendicular to the substrate surface. It is preferably applied in a cooling, spraying facility.

Spraying of ionizing air Spraying of ionizing air of positive polarity in the direction parallel to the substrate surface is usually carried out by the following method. As shown in FIG. 1, the molded substrate taken out from the molding machine is placed on a cooling stage installed inside a clean booth, and the substrate surface is held in a horizontal plane direction or a vertical direction, preferably in a horizontal plane direction. As shown in FIG. 2, when the substrate surface is held horizontally, the positively charged ionized air is blown in parallel with the horizontally held substrate surface on the cooling stage to remove the substrate surface. Elimination of static electricity is achieved efficiently without deteriorating the sled.

The following is a description with reference to the accompanying drawings. In the figure, 1 is an injection molding machine, 2 is a mold (with a stamper attached),
31 is a substrate take-out machine, 32 is a substrate reversing machine, 33
Is a substrate transfer machine, 4 is a cooling stage, 5 is a substrate takeout machine, 6 is an air supply machine, 7 is a clean booth, 8 is an ionizer, and 9 is a substrate. As shown in FIG. 1, from the injection molding machine (1) to the substrate take-out machine (3)
The molded substrates taken out by the multiple cooling stages (4) installed in the clean booth (7).
In the first stage, the substrate is taken out of the cooling stage (4) by the substrate take-out machine (5) from the last stage, and cooling and static elimination are performed. Although the number of stages of the cooling stage (4) shown in the figure is 16, an appropriate number is actually selected according to the cooling speed, the moving speed of the substrate and the like.

In the present invention, in designing the cooling / static elimination process, while the molded substrate passes through the plurality of cooling stages (4) from the first stage to the last stage, the substrate surface is substantially horizontal. Be maintained at
Receiving the flow of down-blowing cooling air from the direction perpendicular to the substrate surface, and the flow of ionizing air for removing the positive polarity along the upper and lower surfaces of the substrate from a direction substantially parallel to the substrate surface. It is preferable to receive. As the cooling air for down-blowing from above the clean booth (7), discharged air or ionized air may be used, but it does not have to have a function of completely removing static electricity on the substrate surface. The down-blowing flow need only have the function of cooling the substrate, and in order to completely eliminate static electricity only by this flow, the down-blowing air volume must be increased or the air outlet must be brought close to the substrate. As a result, the substrate is non-uniformly cooled, and the warpage of the substrate is deteriorated. Therefore, in the present invention, the flow of the positively charged ionized air along both upper and lower surfaces of the substrate (9) held horizontally on the cooling stage is blown from a direction substantially parallel to the substrate surface. Thus, the static elimination can be efficiently achieved without deteriorating the warpage of the substrate. Here, in order to generate ionized air having a positive polarity, an air supplier (6) and an ionizer (8) provided for each stage are used in the figure. Adjust the polarity of the ionizer (8) to an appropriate positive charged voltage value, and then supply the air supply (6).
By adjusting the air flow rate of the molded substrate to an appropriate value, the desired charge removal of the molded substrate is achieved. The molded substrate taken out from the cooling stage (4) is usually transported to the following step of laminating a dye recording layer and the like.

Application of Dye Usually, a dye solution prepared by dissolving an organic dye in an organic solvent is applied by a spin coating method so as to fill the groove formed on the signal surface of the molded substrate. . The spin coating method is generally carried out according to the following procedure using a spin coating device including a coating liquid applying device (dispensing nozzle), a spinner head, a shatterproof wall, and an exhaust device. First, the molded substrate is placed on the spinner head, and then, while rotating the spinner head by the drive motor, on the surface of the inner peripheral portion of the substrate, preferably within 2 to 3 mm from the innermost peripheral edge of the groove. The coating liquid is supplied to the position from the nozzle of the coating liquid applying device. The coating liquid supplied onto the substrate is radially cast on the outer peripheral side by centrifugal force to form a coating film. During the spin coating operation, a dry gas such as air is introduced through an opening (gas inlet) provided above the shatterproof wall, the gas is circulated on the coating film, and exhausted from below the spin coating device. . By the circulation of this gas, the solvent is removed from the coating film and the coating film is dried. If necessary, the substrate is put into a drying oven called baking to remove the residual solvent as completely as possible.

In the case of a write-once optical disc, the dye is
A dye having an absorption region in the laser light wavelength range (300 to 850 nm) is selected. Specifically, azo dyes, cyanine dyes, phthalocyanine dyes, azurenium dyes, squarylium dyes, polymethine dyes, pyrylium dyes, thiopyrylium dyes, indoaniline dyes, naphthoquinone dyes, anthraquinone dyes, triallylmethane dyes, aminium dyes, diimonium dyes, Examples thereof include metal chelate dyes composed of an azo ligand compound and a metal, metal complexes and the like, and mixtures thereof. Preferred are organic dyes of azo type, cyanine type and phthalocyanine type. These dyes have excellent signal sensitivity, are easily dissolved in a solvent, have good light resistance, and make it possible to obtain a high-quality write-once optical disc.

Specific examples of the organic solvent for the dye solution include esters such as butyl acetate and cellosolve acetate,
Methyl ethyl ketone, cyclohexanone, ketones such as methyl isobutyl ketone, chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane, chloroform, amides such as dimethylformamide, hydrocarbons such as cyclohexane, ethers such as tetrahydrofuran, ethyl ether, dioxane, ethanol. , Alcohols such as n-propanol, isopropanol, n-butanol and diacetone alcohol, fluorine-based solvents such as 2,2,3,3-tetrafluoropropanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether And other glycol ethers. These solvents may be used alone or in combination of two or more in consideration of the solubility of the dye used. Preferably 2, 2, 3,
It is a fluorine-based solvent such as 3-tetrafluoropropanol, octafluoropentanol, and dibutyl ether.

Further, a reflective film such as Ag or Au is formed on the surface of the dye recording layer by a sputtering method to form a reflective layer, and if necessary, a protective layer is formed by coating the surface of the reflective layer with a protective film. A laminated body is obtained. In the case of a CD-R, it is formed of a single plate, but in the case of a DVD-R, it is possible to achieve high density by sticking two of the above substrates together.

[0042]

EXAMPLES The present invention will be described below according to examples, but the present invention is not limited to the scope of the following examples.
In the examples, all parts,% and ppm are based on weight unless otherwise specified.

[Example 1] 1. Preparation of Polycarbonate Pellets In a stainless steel 20 L vertical stirring reactor equipped with a condenser, 2283 g (10.0 mol) of bisphenol A, 2290 g (10.7 mol) of diphenyl carbonate, and 58.5 g (0.39 g of 4-t-butylphenol) were added.
Mol, 3.9 mol% with respect to bisphenol A), and 0.01 N sodium hydroxide 0.7 mL (7 × 10 ⁻⁶ mol with respect to 1 mol of bisphenol A) as a catalyst were charged, and nitrogen substitution was performed. This mixture was melted in the first tank at 220 ° C. for 40 minutes to melt the raw material monomers and then in the second tank.
60 minutes at 0 ° C / 13.3kPa, 240 ° C / in the third tank
60 minutes at 2.00 kPa, 270 ° C / 66.7 in the fourth tank
The reaction was carried out at Pa for 60 minutes, and butyl p-toluenesulfonate (2 times the molar amount of sodium hydroxide used as the catalyst) was added as a catalyst deactivator to terminate the reaction. As a result, an aromatic polycarbonate having a viscosity average molecular weight of 16,000 was obtained and cut into pellets with a cutter. An optical disc substrate was molded using the obtained pellets under the following conditions.

2. Manufacture of Molded Substrate The obtained pellets were injection-molded under the following conditions to obtain a molded substrate. Molding machine: Sumitomo Heavy Industries DISK3 Mold: 12 cmφ CD, DVD mold Molding substrate thickness: 1.2 mm Stamper groove depth: 160 nm Stamper groove pitch: 0.80 μm Maximum setting temperature of molding machine cylinder: 360 ° C Stamper Set temperature of the mold on the side where is installed: 1
30 ° C. Injection time: 0.1 seconds Cooling time: 7.0 seconds Screw rotation speed: 360 rpm Screw diameter: 25 mmφ Clamping force: Injection, 20 T during holding pressure, 25 T during cooling

3. Preparation of write-once type optical disk The substrate molded under the above conditions was cooled in 18 cooling stages after the molded substrate was taken out from the mold. Ionizer (Hugele Electronics MO
DEL 430 DC type ionizer) was installed at the position shown in FIG. 2 so that the direction of blowing was parallel to the substrate surface. Polarity: Positive output voltage: +6.0 kv Air flow rate: 130 L / min Air pressure: 0.1 MPa Distance between substrate end face and ionizer: 20 cm While rotating the obtained substrate at 50 rpm, 3 mm inward from the innermost circumference of the groove A 5% solution of an azo dye, octafluoropentanol, was dropped onto the inner peripheral portion of the nozzle through a nozzle. The coating liquid supplied onto the substrate has a rotation speed of 5000r.
By raising the pressure to pm, the coating solution was radially cast on the outer peripheral side to form a coating liquid filled with the grooves. Air was introduced through an opening (gas inlet) provided above the coater and exhausted from below the spin coater to volatilize the solvent. After that, the substrate was put into a drying oven kept at 95 ° C. and dried for 15 minutes to remove the residual solvent, thereby completing the formation of the dye recording layer. After that, A on the surface of the dye recording layer
g was sputtered and further coated with a protective film to obtain a CD-R type write-once type optical disc.

4. Evaluation Method For each of the obtained molded substrate or write-once type optical disc, the following items were measured using 5 substrates. The results are
Shown in 1. (1) Water drop contact angle The measurement was performed by the method described in the text. (2) Birefringence oak automatic birefringence measuring device (Oak Co., Ltd., trade name A
DR-130N) was used, the tilt direction of the substrate was changed in two ways, and the measurement was performed with a He-Ne laser beam having a wavelength of 632.8 nm. The maximum absolute value at four points in the radial direction was defined as birefringence. (3) Tangential Tilt Admon Science's automatic warp angle measuring device was used to measure 16 points (8 points at approximately equal intervals on the orthogonal diameter) of the substrate immediately before the dye application, and the warp angle in the tangential direction. It was measured and the maximum absolute value was displayed as the tangential tilt.

(4) Presence or absence of deformation of droplets immediately after dropping The dyes of the dye recording layer described in Table-1 were dissolved in octafluoropentanol to prepare a 5% solution.
The prepared solution was dropped by a microsyringe on the surface of the inner peripheral portion of the molded substrate that was quickly taken out after cooling, and the shape of the droplet was visually observed to confirm whether the droplet was deformed (whether it was a perfect circle or not). Deformation). (5) Presence or absence of bright defect Visually observing the dye recording layer formed on the substrate after dye coating, and defining a portion where the dye is partially thin as a bright defect,
The presence or absence thereof was investigated.

[0048]

Example 2 Example 1 was repeated except that polycarbonate was obtained without adding pt-butylphenol and 6000 ppm of pentaerythritol tetrastearate was mixed with the obtained polymer pellets.
An optical disc was obtained in the same manner as in. The evaluation results are shown in Table-1.

Example 3 An optical disk was obtained in the same manner as in Example 1, except that the cyanine dye solution was used instead of the azo dye solution. The evaluation results are shown in Table-1.

Example 4 An optical disk was obtained in the same manner as in Example 1 except that the phthalocyanine dye solution was used in place of the azo dye solution. Table of evaluation results
Shown in 1.

[Embodiment 5] In Embodiment 1, 290 ° C./3 in the fourth tank
An optical disc was obtained in the same manner as in Example 1 except that the reaction was performed at 2 Pa for 60 minutes. The evaluation results are shown in Table-1.

[Sixth Embodiment] In the fifth embodiment, the substrate thickness is 1, 2 mm.
In the same manner as in Example 5, except that the substrate after dye coating and Ag sputtering was bonded to the substrate before dye coating with an acrylic adhesive instead of 0.6 mm.
A DVD-R write-once optical disc was obtained. The evaluation results are shown in Table-1.

[0049]

Comparative Example 1 An optical disk was obtained in the same manner as in Example 1 except that pt-butylphenol was not used. The evaluation results are shown in Table-1.

Comparative Example 2 In Example 1, 320 ° C./1 in the fourth tank
An optical disc was obtained in the same manner as in Example 1 except that the reaction was performed at 2 Pa for 60 minutes. The evaluation results are shown in Table-1.

Comparative Example 3 An optical disk was obtained in the same manner as in Example 1 except that nonylphenol was used instead of pt-butylphenol. Table 1 shows the evaluation results.
Shown in.

Comparative Example 4 An optical disk was obtained in the same manner as in Example 1 except that the blow was not used.
The evaluation results are shown in Table-1.

Comparative Example 5 An optical disk was obtained in the same manner as in Example 1 except that the blow polarity was negative. The evaluation results are shown in Table-1.

Comparative Example 6 An optical disk was obtained in the same manner as in Example 1 except that the blowing direction was perpendicular to the substrate. The evaluation results are shown in Table-1.

[0050]

[Table 1]

From the results shown in the above table, in Examples 1 to 6 satisfying the requirements of the invention, the birefringence and the warp (tangential tilt) were small, and the dye coating failure (droplet deformation immediately after dropping). ) And an excellent optical disc substrate or optical disc without bright defects. This is the same for both the CD-R type (Examples 1 to 5) in which the substrate is a single plate and the bonded DVD-R type (Example 6). Further, similar results are obtained even if the water droplet contact angle is reduced to a proper value by the additive (Example 2: Comparative Example 3). However, the object of the present invention cannot be achieved when the predetermined requirements are lacking. That is, regarding the polycarbonate resin used, when the viscosity average molecular weight is too large (Comparative Example 2), the birefringence remarkably increases, and when the contact angle of water droplets is too small (Comparative Example 1), defective dye coating occurs. If it is too large (Comparative Example 3), bright defects will result. Regarding the spraying of the ionized air, if this is not performed at all (Comparative Example 4) or the ionized air having a negative polarity is used (Comparative Example 5), defective dye coating cannot be avoided, and the spraying direction is changed. If it is perpendicular to the substrate surface (Comparative Example 6), the warp increases.

[0052]

According to the present invention, the warp of the substrate is small,
It is possible to provide a method for manufacturing a write-once optical disk substrate and a method for manufacturing a write-once optical disk in which the birefringence of the substrate is small, there are no bright defects, there is no dye coating failure, and there is no dust adhesion on the surface.

[Brief description of drawings]

FIG. 1 is a schematic view showing a manufacturing process of a substrate.

[Fig. 2] Layout plan of static eliminator

[Explanation of symbols]

1. Molding machine 2. Mold 31. Substrate takeout machine 32. Substrate reversing machine 33. Substrate transfer machine 4. Cooling stage 5. Substrate takeout machine 6. Air supply machine 7. Clean booth 8. Ionizer 9. substrate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyoshi Maruyama             5-6 Higashi-Hachiman 5-2, Hiratsuka City, Kanagawa Prefecture             Ryo Engineering Plastics Stock Association             Company Technology Center (72) Inventor Haruhiko Kurokawa             5-6 Higashi-Hachiman 5-2, Hiratsuka City, Kanagawa Prefecture             Ryo Engineering Plastics Stock Association             Company Technology Center F-term (reference) 5D029 JA04 KA07 KC09 RA03 RA07                       RA08                 5D121 AA02 AA07 GG30

Claims (3)

[Claims] 1. A molded substrate having a groove formed on a signal surface by injection molding of a polycarbonate resin having a viscosity average molecular weight of 10,000 to 23,000, which is produced from an aromatic dihydroxy compound and a carbonic acid diester by a transesterification method. A method of manufacturing a write-once type optical disc substrate, wherein a dye recording layer is formed by coating a dye on the surface of the recording medium, wherein the water drop contact angle measured on the signal surface before formation of the dye recording layer is 77 °.
A method for manufacturing a write-once type optical disc substrate, characterized in that ionized air having a positive polarity of 85 ° or less and before applying a dye is blown in a direction parallel to the substrate surface. 2. A dye recording layer is formed by applying a dye solution in which an azo-based, cyanine-based or phthalocyanine-based organic dye is dissolved in an organic solvent to the signal surface. Item 2. A method for manufacturing a write-once optical disc substrate according to Item 1. 3. A method of manufacturing a write-once optical disc obtained from the write-once optical disc substrate according to claim 1, wherein two molded substrates having a thickness of 0.2 mm or more and 0.6 mm or less are formed. A method of manufacturing a write-once type optical disc, which has a structure in which the dye recording layer is attached inside.